Consider the following statements relating hydrostatic forces on submerged surface :

1. The pressure centre is always below the centroid of any plane submerged surface that is not horizontal.
2. Total force on a curved surface is the product of the average force and the submerged area.
3. The magnitude of hydrostatic pressure at a particular depth is a function of the shape of the surface.
4. The vertical component of force on a body completely submerged in a static reservoir of fluid is equal to the weight of the fluid displaced by the body.

Of these statements